POS0922 RECOMBINANT HUMAN HYALURONIDASE-FACILITATED SUBCUTANEOUS IMMUNOGLOBULIN FOR IDIOPATHIC INFLAMMATORY MYOSITIS: A MULTICENTER OBSERVATIONAL STUDY
Authors: A. Palermo, A. Bettiol, M. L. Urban, A. Barilaro, M. G. Danieli, M. Capassoni, S. Guiducci, C. Campochiaro, L. Dagna, V. Canti, P. Rovere-Querini, C. Cardelli, M. Mosca, G. Emmi
Journal: Annals of the Rheumatic Diseases (2022)

Background The spectrum of idiopathic inflammatory myositis (IIM) includes a heterogeneous group of diseases characterized by chronic inflammation of skeletal muscle, often associated with skin, joints, lungs, esophageal, gastrointestinal and cardiac involvement. Conventional treatment for IIM is based on glucocorticoids and immunosuppressants. Moreover, intravenous immunoglobulin (IVIg) has emerged as a promising steroid- and DMARD-sparing treatment for myositis [1]. However, the long-term use of IVIg is complicated by the fact that the intravenous route requires in-hospital drug administration, which not only influences patients’ quality of life, but is also associated with an increased risk of systemic adverse effects, difficulties in venous access over time, and high costs [2]. On these bases, administration of subcutaneous Ig (SCIg) by a programmable pump has been considered as a possible alternative to IVIg. Recombinant human hyaluronidase-facilitated (hf)-SCIg is currently approved for the use in patients with primary immunodeficiency disorders, while its efficacy and safety in myositis disorders is limited [3]. Objectives This multicenter retrospective observational study is sought to evaluate the effectiveness and safety of recombinant human hf-SCIg in patients with IIM treated at different referral centers. Methods A multicenter, retrospective, cohort study was conducted on adult patients diagnosed with IIM according to the EULAR/ACR classification criteria [4] treated with recombinant human hf-SCIg according to routine clinical practice. The effectiveness of this treatment was assessed in terms of variations in the Medical Research Council (MRC) score, creatine kinase values, inflammatory parameters, and daily prednisolone dosage. Safety data were also collected. Results Twenty-three patients with IIM treated with hf-SCIg were included (16/23 females, 70%; median age at diagnosis of 61 years (IQR 43-65)). In most patients (22/23, 96%), IIM had been initially treated with high-dose corticosteroids (+/- synthetic or biologic DMARDs), and 20/23 patients (87%) had received previous IVIg treatment (in 12 for remission induction and in 8 for maintenance). Hf-SCIg were introduced after a median time of 2 years (1-4) from the diagnosis of IIM, mostly for remission maintenance (18/23). Hf-SCIg was started in combination with oral corticosteroids in 19/23 [83%, at a median dose of 5 mg/day (4-12.5)] and/or with traditional or biologic DMARDs (18/23, 78%). At time of hf-SCIg introduction, the median MRC score was 4 (3-4) and the median creatine kinase level was of 134 U/L (44-243). After 6 months of treatment, the median MRC score was 4 (3-5); no patient discontinued hf-SCIg, and only one experience a mild adverse event. Conclusion Hf-SCIg seems effective to maintain remission in a high proportion of IIM patients, while showing a good safety profile in the first 6 months of treatment. References [1]Oddis. Treatment in myositis. Nat Rev Rheumatol 2018 [2]Danieli. Subcutaneous IgG in the Myositis Spectrum Disorders. Curr Rheumatol Rev. 2018. [3]Wasserman. Recombinant human hyaluronidase-facilitated subcutaneous infusion of human immunoglobulins for primary immunodeficiency. JACI.2012. [4]Lundberg. 2017 European League Against Rheumatism/American College of Rheumatology classification criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups. ARD. 2017 Table 1. Effectiveness and safety of hf-ScIG treatment in a cohort of patients with IIM hf-ScIg beginning 3 months 6 months N patients with available follow-up data 23 20 * 19* MRC score § 4 (3-4) 4 (4-5) 4 (3-5) Creatine kinase, U/L § 134 (44-243) 118 (77-308) 130 (84-222) ESR, mm/h § 21 (15-28) 30 (25-43) 31 (23-39) CRP, mg/dl § 0.2 (0.1-0.5) 0.3 (0.1-0.5) 0.3 (0.1-0.3) Prednisolone dosage, mg/day § 5 (4-12.5) 7.5 (5-10) 5 (5-7.5) Adverse events - NA 1 ** *none discontinued **One infusion site reaction § median value (IQR) CRP=C reactive protein; ESR=erythrocyte sedimentation rate Disclosure of Interests None declared